Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
using ll = int_fast64_t;
using P = std::pair<ll,ll>;
using PP = std::pair<P,ll>;

int main(){
	int h, w, ans = 0;
	scanf("%d %d", &h, &w);
	std::vector<std::vector<bool>> fie(h+2, std::vector<bool>(w+2, true));
	for(int i=1; i<=h; i++){
		char s[w+1];
		scanf("%s", s);
		for(int j=1; j<=w; j++){
			fie[i][j] = (s[j-1]=='#');
			ans += (s[j-1]=='.');
		}
	}
	
	int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};	

	int dist = INT_MAX;
	std::queue<PP> que;
	que.push(PP(P(1,1), 0));
	while(!que.empty()){
		P p = que.front().first;
		int x=p.first, y=p.second, d=que.front().second;
		que.pop();
		if(x==h && y==w) dist = d;
		if(fie[x][y]) continue;
		fie[x][y] = true;
		for(int i=0; i<4; i++){
			int nx = x + dx[i], ny = y + dy[i];
			if(!fie[nx][ny]) que.push(PP(P(nx,ny), d+1));
		}
	}

	if(dist==INT_MAX) puts("-1");
	else printf("%d\n", ans-dist-1);
	return 0;
}